The invention pertains generally to electromagnetic moving magnet motors, and more particularly to moving magnet motors having an integral moving magnet and back iron flux return path structure.
In moving magnet motors, a thin magnet is moved in a linear direction by interaction of magnetic forces between the moving magnet and the stationary stator structure. A coil or coils wound about the stator structure is energized by an applied voltage to develop a magnetic field that interacts with the movable magnet. The magnet is propelled in a linear direction by the magnetic field generated by the stator structure. The same concepts apply to rotary motors except the electromagnetic force emanating from the stator interacts tangentially with the moving magnet structure propelling the magnet about an axial pivot.
Heretofore, stator structures have been constructed with three or more poles. In addition, the previous stator designs always maintained a stationary back iron which may or may not provide a return path for the magnetic flux. Such moving magnet motors with stationary stators have been disclosed in U.S. Pat. No. 4,775,908, Swiss Patent Application No. CH 669,064 A5, and French Patent Application No. 89/08051. These aforementioned designs incorporate three major components: a pole piece, coil or coils, a moving magnet, and a back iron structure. The result is a significant overall space requirement for the motor.
The overall space requirement for moving magnet motors has become increasingly critical. A number of applications, such as small disk drives, require extreme miniaturization that is not feasible using the embodiments of the apparatus described in the prior art.
The objective of the current invention is to provide a useful solution to the overall space problem and to simplify overall motor design. The objective is attained by attaching a back iron which functions as a flux return path portion to the moving magnet, producing a motor with a moving back iron and magnet combination. In addition, the copper per volume ratio is increased resulting in an intensified flux field and a simplified motor design.